1. Field of the Invention
The invention relates to a device for treating lung disease, and more particularly, the invention relates to a device for transferring energy into airway tissue such as that found in the airways of human lungs. This includes heating and applying RF energy to the airway. In the airways of the lung, the transfer of energy into the airway tissue stiffens that tissue or reduces the ability of the airways to constrict. In general the treatment reduces the resistance to the flow of air through the airway.
2. Brief Description of the Related Art
Asthma is a disease in which (i) bronchoconstriction, (ii) excessive mucus production, and (iii) inflammation and swelling of airways occur, causing widespread but variable airflow obstruction thereby making it difficult for the asthma sufferer to breathe. Asthma is a chronic disorder, primarily characterized by persistent airway inflammation. However, asthma is further characterized by acute episodes of additional airway narrowing via contraction of hyper-responsive airway smooth muscle.
Asthma stimuli may be allergenic or non-allergenic. Examples of allergenic stimuli include pollen, pet dander, dust mites, bacterial or viral infection, mold, dust, or airborne pollutants; non-allergenic stimuli include exercise or exposure to cold, dry air.
In asthma, chronic inflammatory processes in the airway play a central role. Many cells and cellular elements are involved in the inflammatory process, particularly mast cells, eosinophils T lymphocytes, neutrophils, epithelial cells, and even airway smooth muscle itself. The reactions of these cells result in an associated increase in the existing sensitivity and hyperresponsiveness of the airway smooth muscle cells that line the airways to the particular stimuli involved.
The chronic nature of asthma can also lead to remodeling of the airway wall (i.e., structural changes such as thickening or edema) which can further affect the function of the airway wall and influence airway hyperresponsiveness. Other physiologic changes associated with asthma include excess mucus production, and if the asthma is severe, mucus plugging, as well as ongoing epithelial denudation and repair. Epithelial denudation exposes the underlying tissue to substances that would not normally come in contact with them, further reinforcing the cycle of cellular damage and inflammatory response.
In susceptible individuals, asthma symptoms include recurrent episodes of shortness of breath (dyspnea), wheezing, chest tightness, and cough. Currently, asthma is managed by a combination of stimulus avoidance and pharmacology.
Stimulus avoidance is accomplished via systematic identification and minimization of contact with each type of stimuli. It may, however, be impractical and not always helpful to avoid all potential stimuli.
Asthma is managed pharmacologically by: (1) long term control through use of anti-inflammatories and long-acting bronchodilators and (2) short term management of acute exacerbations through use of short-acting bronchodilators. Both approaches require repeated and regular use of the prescribed drugs. High doses of corticosteroid anti-inflammatory drugs can have serious side effects that require careful management. In addition, some patients are resistant to steroid treatment. Patient compliance with pharmacologic management and stimulus avoidance is often a barrier to successful asthma management.
Asthma is a serious disease with growing numbers of sufferers. Current management techniques are neither completely successful nor free from side effects.
Accordingly, it would be desirable to provide an asthma treatment which improves airflow without the need for patient compliance.
In addition to the airways of the lungs, other body conduits such as the esophagus, ureter, urethra, and coronary arteries, are also subject to periodic spasms that interfere with their normal function.